People rely heavily on the meanings that they attach to certain objects. A “pipe” may go from one side of a room to the other side, but if it carries jet fuel, it is called a “fuel-line.” Another “pipe” may go from floor to ceiling in the same room, but because it is used to evacuate heat from a steam boiler in a lower floor, it is called a “heat riser.” Design engineers understand the deep meaning of “heat riser” and “fuel line,” and they know that a “heat riser” should not be within close proximity of a “fuel line” lest there be explosion or fire. However, a casual observer might only think of both objects as “pipes.” Data about both pipes may be stored in a computer database, with other attributes, such as length and diameter.
Many interactive, graphical computer software applications process vast amounts of complex three-dimensional model data for presentation on one or more video displays. Such applications include, for example, computer-assisted design (CAD) tools for designing three-dimensional articles, buildings, and vehicles for manufacture, and geographic information system (GIS) tools, which are used to track public transit systems or communications networks. Typically, an individual will use such programs at a workstation or computer terminal, as shown in FIG. 1. As can be seen in FIG. 1, the workstation may have several video displays, arranged at the convenience of the individual, to allow the individual a large display area on which to operate software applications.